Question

how many neutrons does this have? * 19 9 f 9 19 10 -1 28

Explanation:

Step1: Identify mass number and atomic number

The notation $^{19}_{9}F$ means the mass number ($A$) is 19 and the atomic number ($Z$) is 9.

Step2: Use neutron - number formula

The number of neutrons ($N$) is calculated by the formula $N=A - Z$.
Substitute $A = 19$ and $Z = 9$ into the formula: $N=19 - 9$.
$N = 10$.

Answer:

C. 10